Poly(isobutylene-co-isoprene) or IIR, is a synthetic elastomer commonly known as butyl rubber (or Butyl polymer) which has been prepared since the 1940's through the random cationic copolymerization of isobutylene with small amounts of isoprene (usually not more than 2.5 mol %). As a result of its molecular structure, IIR possesses superior air impermeability, a high loss modulus, oxidative stability and extended fatigue resistance.
Halogenation of butyl rubber produces reactive allylic halide functionality within the elastomer. Conventional butyl rubber halogenation processes are described in, for example, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A231 Editors Elvers, et al.) and/or “Rubber Technology” (Third Edition) by Maurice Morton, Chapter 10 (Van Nostrand Reinhold Company © 1987), particularly pp. 297-300.
The development of halogenated butyl rubber (halobutyl) has greatly extended the usefulness of butyl by providing much higher curing rates and enabling co-vulcanization with general purpose rubbers such as natural rubber and styrene-butadiene rubber (SBR). Butyl rubber and halobutyl rubber are high value polymers, as their unique combination of properties (excellent impermeability, good flex, broad damping characteristics, good weatherability, heat resistance, chemical resistance, biocompatibility, co-vulcanization with high unsaturation rubbers, in the case of halobutyl) make them preferred materials for various applications, such as their use in making tire inner tubes and tire inner liners.
The presence of allylic halide functionalities allows for nucleophilic alkylation reactions. It has been shown that treatment of brominated butyl rubber (BIIR) with nitrogen and/or phosphorus based nucleophiles, in the solid state, leads to the generation of IIR-based ionomers with interesting physical and chemical properties (see: Parent, J. S.; Liskova, A.; Whitney, R. A; Resendes, R. Journal of Polymer Science, Part A: Polymer Chemistry 43, 5671-5679, 2005; Parent, J . S.; Liskova, A.; Resendes, R. Polymer 45, 8091-8096, 2004 ; Parent, J. S. ; Penciu, A. ; Guillen-Castellanos, S . A.; Liskova, A.; Whitney, R. A. Macromolecules 37, 7477-7483, 2004). The ionomer functionality is generated from the reaction of a nitrogen or phosphorus based nucleophile and the allylic halide sites in the halogenated butyl rubber to produce an ammonium or phosphonium ionic group respectively. In addition to benefits derived from the butyl rubber, butyl rubber ionomers are also more easily formed into pellets and have enhanced green strength.
Thermoplastics are materials which contain physical, thermoreversible networks imparting excellent physical properties and are widely used in a variety of applications. For example, polyethylenes have good impact resistance, light weight, high tensile strength, good resistance to chemicals, low moisture absorption, ease of processing (e.g. injection moldable) and are FDA approved for direct contact. Polyethylenes are used in detergent, milk and juice bottles, cutting boards, water pipes, molded plastic cases and garden furniture, among others. Polyamides have good durability, high elongation, excellent abrasion resistance, good impact resistance, antimicrobial properties, and good resistance to chemicals. Polyamides are used in rope, fibers, carpets, sports equipment, bristles, low strength machine parts, seat belts and tire cords, among others. Polypropylene has light weight, high tensile strength, excellent abrasion resistance, good impact resistance, good resistance to chemicals and is sterilized using autoclaves. Polypropylene is used in plastic pressure pipe systems, storage containers, bottle caps, appliances (e.g. kettles), car fenders (bumpers) and diapers, among others.
However, despite the success of thermoplastics, there remains a need for improving one or more of the properties of thermoplastics.